Surfaces of aircraft (body, wing, nacelle, and engine), power generation structures (e.g. wind and land based turbines, gas turbines, etc.) or other structures may be subject to environmental erosion conditions that can degrade the performance and/or durability of the structure. These surfaces can be modified to contain geometric features such as riblets for aerodynamic performance enhancement, moisture/ice accumulation prevention, erosion protection, and other reasons.
Aerodynamic performance of symmetrical two-dimensional (2D) riblets with sawtooth, scalloped, and blade cross sections has been extensively studied. Alternative riblet geometries including asymmetrical riblets, hierarchical riblets, and riblets with rounded or notched peaks, have in general, shown no increased benefit. Other 2D riblet shapes studied include alternating brother-sister type riblets and hierarchical riblets with small riblets on top of larger riblets. These studies were largely limited to aerodynamic parameters and failed to consider the effect of erosive field conditions on riblet performance.
To address erosion, a surface may include a hard coating. However, a challenge exists in the design of surfaces that are subject to various erosion conditions since coatings that provide aerodynamic or anti-icing properties may not provide erosion (both rain and grit) protection and, vice-versa, coatings that provide erosion protection may not provide aerodynamic or anti-icing properties.
It is highly desirable to provide a modified surface, such as an airfoil, with a durable riblet array laminate that both withstands erosive conditions and maintains its aerodynamic/anti-icing properties.